Method for drying alcohols and esters



' Nov. 26, 1935. B. T. BROOKS A 2,022,274

I METHOD FOR DRYING `ALcoHoLs ANDESTERS 2 v Fi1ed sepa 15. 1931 ssheets-sheet 1 INVENTOR- A Zelf/dyn Tas Ww/77 'ATTORNEYS Nov-26,1935. lB. T. BRQQKS 2,022,214

\ ATTORNEYS METHOD OR DRYING ALCOHOLS AND `ESTERS Filed sep-t. 15. 1931s sheets-sheet 2 Novi-265 1935. B. T. BROOKS 2,022,274

METHOD FOR DRYING ALCOHOLS AND4 ES'IERSk Filed Sept. 15. 1931sh'eets-Sheet 5 lNVENTOR @ad l/ TTORNEYSW I Patented Nove. 26, 1935METHOD-'FOR ALCOHOLS AND ESTERS Benjamin T. Brooks,

by mesne assignments Company, Wilmington, Delaware Greenwich, Conn.,assignor,

, to Standard Alcohol Del., a `corporation of 12 Claims.

My invention relates tothe drying of solvents and more particularly todrying the common solvent alcohols and their esters such as isopropyl,primary and secondary butyl and primary and secondary amylalcohols andtheir esters.

Upto the present time, the common solvent alcohols have been dried bycontacting themwith anhydrous compounds such as sodium sulphate, coppersulphate, potassium carbonate, and in rare instances, by solid causticsoda or potash. The esters generally have been dried by the use oineutral anhydrous compounds such as sodium sulphate, calcium chlorideland the like. 'I'heA use of such anhydrous solid substances has proved-to be expensive, i eilicient, incomplete, and generally objectionble,due to the diiiculty of contacting all of t e liquid solvent withthe dry .-substances. A-'fu\ her objection to theuse of such soliddrying substances resides in the reconditioning ofA them for reuse. Insuch reconditioning, the substances must ordinarily be reconcentratedand fused to drive ofithe moisture. The fused mass must then be formed'into ,akes or finely 'commlnuted form requiring ex-` pensive apparatusand processes'. The main 'object of myv invention is to eliminate .ftheobjectionable features of the prior methods by, employing a drying agentwhich has not here-e tofore been usedfor this purposeand which obrviates all of the objections of the prior methods as it operatesquickly, efficiently and completely.

In the drawings: Figure l is a view of an apparatus such as may be usedin the continuous operation of my process. Figure 2 is a representationof an apparatus suitable for practising my invention using a continuouscounter-current process.

Figure 3 represents a'. modification of t paratus shown in Figure 2.

My invention is based on the discovery that a very concentrated solutionof caustic alkali, such he apas caustic soda, or caustic potash, or veryconcentrated solutions oi hygroscopic salts such as calcium chloride orzinc chloride, can be employed to remove the moisture from and dry thecommon solvent alcohols and their esters, particularly the acetates.Accordingly, when I refer hereinafter in` they specification and claimsto caustic alkali the same is to be understood to include caustic soda,caustic potash, and their equivalents. It is well known .that alcoholsare more lor less miscible with water and that dilutealkalies willsaponify esters. I have found, however, that the commonsolvent alcoholsand their esters' are not r (Cl. 26o-106) e miscible with concentratedsolutions of alkalies containing over 40% of. alkali, particularly whenemployed at such temperatures that the solutions are substantiallysaturated. Such concentrations of alkali will not saponify esters atordinary temperatures but will remove moisture from such solvents whenadmixed therewith and then separated therefrom.'

This property of the alkali solution of being immiscible with thesolvents appears to be due to a saiting out effect ofthe alkali but I donot wish to be restricted to any particular theory. Since .the solutionof alkali is immiscible with the solvents and has .a diierentspecicgravity, it may be readily separated from the solvents by l5 allowingthe Imixture to stand for a short space .of time whereupon the mixturewill stratify into layers of dry solvent and alkali solution. Myinvention accordingly resides in the treat- .ment'of wet solventalcohols, their esters, or a 20 mixture of alcohols and` esters with asolution of a caustic alkali containing over 40% caustic alkali andpreferably about 50% or a concentrated or substantiallysaturatedsolutionA of a hygroscopic l salt to dry the solvents.I The process isprefer- 25 ably carried out at lowA temperatures ranging from 0 to 20 C.such that the alkali or salt solution is substantially saturatedand yetat such temperatures that the solution is iluid and will ow readily.Incarrying out my process, the 30 amount of water present in the solventis determined, and. an amount of the solution of causticvalkalisufiicient to take up all of the water Without diluting it tobelow 40% is added to and thoroughly admixed with the wet solvent. s The35 l mixture is then allowed to stand, whereupon the r alkali .or saltsolution will rapidly settle to the bottom of the container, separatingfrom the dry solvent, which may. be withdrawn from the top. -Theseparated alkali or salt solution may be re- 40 concentrated and used totreat other wet solvent. The preferred material is a solution of4caustic soda containing about 50% of sodium hydroxide.

The hygroscopic salts, such as calcium chloride of undissolved alkalisuch as the mono'- and dihydrates, insufficient, however, 4to destroythe uidity of the solution. Also, when a substantially saturatedsolution is employed at say 20 C. and becomes diluted somewhat by takingup water from the material treated,` its eillciency may be restored tosome extent by cooling it to say 10 or 0 C. whereby the solution mayagain become substantially saturated.

By this process the alcohol or ester or mixture of the same is quicklyand completely dried. When alcohols are so treated, they dissolveonlynegligible amounts of the alkali which may be recovered by distillation.Furthermore, only negligible amounts of the solvents are absorbed anddissolved in the alkali solution, thereby rendering' it unnecessary toemploy distillation to recover the solvent from the drying. agent. Forexample, when esters 4such as isopropyl,.butyl and amyl acetatescontaining from 10% to 20% of free alcohols are treated by this process,not

more than one-half tol one percent of such alcohols are extracted fromthe mixture treated.

'I'his process is particularly applicable to the drying and purifying ofesters produced by the action of acids such as acetic on alcohols suchas isopropyl, butyl and amyl'. Ihe products resulting from ythis processusually consist of a mixture of ester, alcohol, water and acid. Whensuch product istreated by my process, the acid' is neutralized andremoved simultaneously with the water. When treating solvents containingacids, it is advisable to cool the containing vessel to prevent thetemperature from rising to the point where appreciable saponiiication ofthe esters might result. Such cooling is not always of supply for thesolvent, has a valve I2 and is connected with the conduit 8.: Theconduit is connected to an upwardly extending mixing column I 4containing perforated plates I 8 which `cause the flow of iluidtherethrough to be turbulent, thereby effecting a thorough admixture .ofthe fluids passing therethrough. The column I4 is connected to thesettling tank I8 at a point spaced from the bottom thereof. Any suitablemeans, such as a pump 20 operated from a motor 22 or other suitablemeans, mayV be provided for forcing the uids' through the column I4 andinto the tank I8.

A conduit 24-leads from adjacent the top .of the tank I8 to a pointspaced from the bottom of' a second` settling tank 26. 'Ihe settlingtank 28 isv provided with a draw-off conduit 28 which leads to asuitable storage tank (not shown). Suitable draw-oil conduits 30 and 82provided with valves 34 and 36 respectively lead from the bottoms oftanks I8 and 28 andare connected to the conduit 38 which delivers into asuitable evaporator 48 through-a valve 42. A suitable pump 44 operatedfrom a motor 46 orother suitable means, is provided for forcing liquidthrough .ftheconduit 88 and into the evaporator. The' evaporator isconnected to the storage tank 2 by tank to be reused and means of aconduit 48 provided with a valve Il. A conduit 52 provided with a valve'54 connects conduit 38 to conduit 4. Each oi the settling tanks maybeprovided with a suitable sight glass 88.

My continuous process using the above described apparatus may bepracticed as follows: The valves 8 and I2 are regulated to admit theproper proportions lof lalkali solution and solvent to the conduit 8through which the fluids pass 1o into the tank I8. During their passagethrough the conduit 8 and column -I4 and particularly due to the actionof the plates I6, the two fluids are thoroughly intermixed and thecaustic alkali brought into contact with all portions of the 18 solvent.In the tank I8 the two uids rapidly form into two layers due to thedifference of their specific gravities, and due to the fact that the twoliquids are almost completely immiscible. The top layer, whichcomprisesr` the solvent con- 20 taining a small amount of entrainedalkali solution is drawn oif through conduit 24 into the second settlingtank 26 wherein a complete separation of the two fluids takes place. Thedried suitable place of storage.

The solution of alkali settles to the bottoms of thetanks I8 and 26 fromwhich it isdrawn 0l! through conduits 30. 32 and 38 and passed into theevaporator 40, where itis reconcentrated. 30 The reconcentrated alkalipasses to the storage again passed through .the

cycle.

When the solvent contains only small amounts of water, it may becomenecessary to use large 35` excesses of the alkali solution in order tocause all portions ofthe solvent to be contacted with the alkali. Insuch case, the alkali will not become so diluted by the extracted wateras to become useless for my purpose-and hence may be 40 recycled one ormoretimes without being reconcentrated. For this purpose the branchconduit 52 and valve i4 are provided; This branch conduit 52 and itsvalve may also be used for more closely regulating the degree ofconcentration as, by this means, part of the diluted alkali fromk -thesettlers may be admixed with the concentrated alkali ilowing from thestorage tank 2.

While in Figure 1, I have shown and have described the use of twosettling tanks, it will be appreciated that I may use a lesser or alarger number. Where only one settling tank is used the flow of liquidtherethrough must be regulated so that a substantially completeseparation of the alkali and the solvent takes place therein. 55 Byusing two settling tanks 'the flow of liquid through the nrst tank mayproceed at such a rate that a. complete separation does not takeplaceand any alkali solution carried through such tank by the solvent willsettle in the second tank. While I may use three or more settling tanksI prefer to use only two, as this permits a more complete mixture ofvthe liquids in the mixing column.

Insome instances, I have found it to/be prefer- `able to employ theapparatus such as disclosed in Figures 2 and 3, operating under thecontinuou's' counter-current flow principles. In the apparatus asdisclosedin Figure 2, alcohol or ester is admitted to the tank 60provided with perforated plates 82 from a suitable conduit 64 connectedwith a source of supply, not shown. The

.solvent passes upwardly through the tank and the perforated plates andoutwardly from the top through the conduit 66 to another similar 'I5centrated alkali into the storage tank 80 from.

tank`68, also provided with perforated .plates 10. 'I'he solvent passesupwardly through the tank 68 through the perforated plates 10' andoutwardly through al conduit 12 to a point spaced from the bottom oftank 14 provided with .perforated plates 16. The solvent passes upwardlythrough this tank 14 and the plates 16 and outwardly from the topthereof through a conduit 18 to a suitable storage tank, not shown. Asolution of caustic alkali is drawn off from the storage tank 80 throughthe conduit 82 'provided with a valve valve 94 and is forced upwardlythrough the con-,

duit 96 vby means of the pump' 98 or other suit able means, operated bya motor or other suitable means 99 and is forced through the rose |00 orother suitable distributing device positioned above the level of thesolvent in'tank 68 wherein the same action takes place as in tank 14..The settled alkali from this 'last mentioned tank is drawn oil throughconduit |02 provided with valve |04 and is forced upwardly throughconduit |06 by means of pump |08 operated by a motor or other suitablemeans |0- and outwardly through the rose or other suitable distributingdevice |2 in the form of a spray above the level of the solvent in tankwherein it contacts and intermixes with more solvent in the same manneras heretofore described with relation to tank 14 and settles to thebottom of this tank. The settled alkali in tank 60 is drawn off throughcon- .duit ||4 provided with valve ||6 and is passed to I-by means ofpump |26 operated by-a motor or other suitable means |28 which forcesthe conwhich it is drawn off to be again passed through the cycle.

conduits 82 and 86 or storage tank `80 may be provided with any suitablemeans for warming the alkali solution.

It will be noted that in this process, using the Iabove describedapparatus, the very wet solvent is treated with a relatively dilutesolution ofv the almofst dried-solvent is then treated with-thev mostconcentrated solution. of alkali in tank 14. While it is not necessaryto always use warmingl and cooling devices asdescribed I have found`that the use of such devices is sometimes prefer. able. l By the use ofsuch devices avery-concentrated solution of caustic alkalicontaining-.crystals of the mono-hydrate and di-hydratemay be stored inthe storage tank 80 and by heating such l storage tank and the conduitleading therefrom- 75| to the desired amount such highly concentratedThe conduits 96 and |06 may be pro. vided with suitable cooling means ifdesired, andv solution can be 'made freely iiuid sov that it may bepassed through the pump 88 Vand ldistributor 80. On this highlyconcentrated solution passing through the tank 14 it becomes somewhatdiluted by means' of the water removed from the solvent in such tank andthen by cooling thisl somewhat diluted alkali as it passes throughconduit.96 its eiliciency is restored prior to its ad- -mission to tank68.- On passing througlntank 68 the solution of alkali again becomessomewhat diluted and by further coolingthe same as it passes throughconduit |06'its eiliciency is again at least partially restored beforeit is admitted. to tank 60. It will be readily appreciated;that by theprocess above described the wettest solvent is treated with the mostdilute alkali and the driest solvent is treated with the ymostconcentrated or saturated'alkali, thereby obtaining a very efficient andcomplete drying of the solvent, using a continuous counter-currentprocess.

Figure 3 shows a modification of the apparatus shown in Figure 2. Inthis Figure 3, solvent from .any suitable` source is forced throughconduit |30 and into a mixing column |32 similar in all respects to themixing columnl |4 shown in Fig- 25g ure 1, and in which the solvent isintimately mixed with a concentrated solution of alkali. 'Die mixedliquids flow from the top of the column |32 into a suitable settlingtank |34 similar in all respects to settling tanks shown in Figure 1. 30i Partly dried solvent is drawn off from the top of this tank throughconduit |36 and iiows through mixing column |38 where it is mixed with anew solution of alkali. The migced iluldsv pass off from the top ofcolumn |38 through the conduit 35i;

|40 into the settling' tank |42. Partially dried vsolventis drawnofl"from the top of this settling tank |42 through conduit |44 and passesthrough the mixing-column` |46 where it is mixed with of alkali. Themixed fluids are drawn oiI from the top of this column through `conduit|48 to settling tank |50. The completely dry solvent is drawn ci fromthe tcp of this .last mentioned settling tank through conduit |52 to asuitable 45..;

storage tank (not shown). A suitable vstorage tank |54 for the alkalisolution -is provided from, which alkali is drawn off through conduit|66 provided with valve |58 by means of pump |60 operated by a motor orother suitable means |62 50. f

which forces the concentrated alkali solution through conduit |64 tocolumn |46 wherein it is mixedwith nearly dry solvent. The alkalisettling in tank |,60 is drawn of! through con- 1 duit |66 provided withvalve. |68 by means of 55.'.

pump |10 operated by a motor yor other suitable means |12 and forcedupwardly through conduit |68 and column |38 wherein it is mixed withpartially dried solvent. 'I'he alkali solution settling in tank. |42 `isdrawn on from the bottom 60a thereof through conduit |14 provided withvalve |16 by meansof pump |10 operated by a motor or other suitablemeans |80 and. upwardly through conduit |82and column |32-wherein it ismixed with fresh wet solvent and flows throught heating coil |90 oryother suitable meansfor re- 70 concentrating thesolution of alkali.` Aconduit |92 adjacent the top of concentrater J 88 is provided toI permitsteam and water vapors to pass oil Afrom the concentraton Theconcentrated alkalimisldrawn off fromthe concentrator, by

means of conduit |94 provided with valve |96 by means of pump |98operated by a motor or other suitable means 200 which causes theconcentrated solution to flow through conduit 2|I2 andinto storage tank|54. As in the apparatus illustrated in Figure 2 the storage tank |54and conduit |56 may be heatedby any suitable means and the conduits |68and |82 and columns |38 and` |32 may be cooled -by any suitable means.The heating and cooling means .are provided ior-the same purposes andmay be employed in the same way as those heretofore described inrelation to the apparatus shown in Figure 2. The apparatus of Figures 2and 3 operate under the same general principles and the use of one orthe other will depend largely upon the materials being treated and thecost of manufacture in the locality in which they are usedJ While I haveshown and described specific apparatus and the manner oi operating thesame for practising my' invention, it will be understood that suchdescription is solely ,.for the purpose of illustration vand that otherapparatus may be remployed and that shown and described may be modifiedin many ways. It will also be understood that many modifications may bemade in v the manner-of practising my invention without departing fromthe principles and spirit thereof. Accordingly, the scope of myinvention is to be limited solely by the following claims and the priorart.

I claim: Y

1. The method oi drying organic alcohols and carboxylic acid esters oi 3or more carbon atoms, which comprises tr ating a compound of the groupconsisting ozorganic alcohols and carboxylicv esters of ee or morecarbon atoms with a concentrat aqueous solution of caustic alkali andseparating thedried compound.

2. Method according to claim 1, in which the alkali solution containsover 40% of alkali.

3. The method of drying organic alcohols and carboxylic acid esters of 3or more carbon atoms,

which comprises treating a compound 'of the group consisting of organicalcohols and carboxylic esters o'i' three or more carbon atoms with aconcentrated solution of caustic alkali immiseible with the compound tobe dried, and

separating the dried compound from thealkali process, which comprisescontinuously mixing a solvent of. the group consisting oi' organic'alcohols and carboxylic esters of three or more carbon atoms with aconcentrated aqueous solution of alkali, separating the solvent from thesolution of alkali andrecycling the solution ot alkali.

6. 'Ihe method ot'drying organic alcohols and carboxylic acid esters ofthree or more carbon* atoms adapted for use as solvents, in a cyclicproc. ess, which comprises continuously admixing a stream of aconcentrated aqueous alkali solution with a stream of asolvent of thegroup consisting of organic alcohols and carboxylic esters oi' three ormore carbon atoms,continuousiy passing said mixture into a settlingchamber, continuously .....drawing oir separated dried solvent from saidchamber 'and'continuously drawing oi'i settled alkali solution from saidchamber and returning j it to the cycle to be admixed with the stream otsolvent.

'1. The method of drying organic alcohols and carboxylic acid estersofthree or more carbon atoms adapted for use as solvents, which 'com-l Iprises contacting a solvent of the groupA consisting of organicalcoholsandcarboxylic esters of three or more carbon atoms with aconcentrated aqueous substantially saturated solution of caustic alkali,separating the solution of caustic 10 alkali from the solvent, coolingthe solution oi caustic alkali to a temperature where it -becomessubstantially saturated, and contacting new portions of the solvent withthe cooled solution. y

8. The method of drying organic alcohols and l5 carboxylic-acid estersof three or more carbon atoms adapted for use as solvents, whichcomprises passing 'a solvent ofthe group consisting of organic alcoholsand carboxylic esters of three or more carbon atoms in a continuous nowthrough a l0 suitable apparatus and. continuously passing a.concentrated aqueous solution oi caustic alkali through the apparatuscountercurrent to the ilow of the solvent and in intimate contacttherewith.

9. 'I'he method of drying organic alcohols and 25 carboxylic acid estersof three or more carbon atoms adapted for use as' solvents, whichcomprises passing a solvent of the group consisting of organic alcoholsand carboxylic esters of three or more carbon 'atoms in acontinucusfilow through 80 y a suitable apparatus, continuously passinga conwith, withdrawing dried compound from one `end 85 of the apparatus,withdrawing diluted solution of. caustic alkali lfrom the other end ofthe apparatus,

i'econcentrating the -diluted solution` of caustic alkali and returningit to the cycle.

10. In a process of drying organic alcohols and 40 carboxylic acidesters of three or more carbon atoms adapted foruse las solvents, whichcomprises passing a solvent or the group consisting of organic alcoholsand carboxylic esters of three or more carbon atoms successively througha series of settling tanks; mixing a concentrated aqueous solution ofcaustic alkaliwith the compound just prior to passing it into the lasttank in thesaid series, withdrawing the settled diluted solution ofcaustic alkali from the bottom-oi each tank in the series except theilrst and admixing it with the solvent entering the next preceding tankand withdrawing the settled diluted solu-v tion from the nrst tank ofthe series.l

I1. In a process of drying organic alcohols and' 65 carboxylic acidlesters of three or more carbon atoms adapted foruse as solvents, whichcomprises Apassing a solvent or the group consisting of organic alcoholsand carboxylic lesters of three or more carbon atoms successivelythrough a 60 series of settlingtanks, mixing a concentrated aqueoussolution ot caustic alkali with the solvent Just prior to passing itinto the lasttank in the said series, withdrawing settled dilutedsolution of caustic alkali from the bottom of each tank in the seriesexcept the nrstand admixing it Awith the compound entering the nextpreceding prises a solvent of the group consisting oi! organic alcoholsand carboxylic esters of three or more carbon atoms successively througha series of settling tanks, mixing a concentrated aqueous solution ofcaustic alkali with the solvent just prior to passingit into the lasttank in the said series, withdrawing settled diluted solution ofcausticalkali from the bottom of each tank in the series except the rstand admixing it with the solvent entering the next preceding tank,withdrawing settled diluted solution from the rst tank oi' the series,and cooling the settled diluted solution otcaustic alkali withdrawn fromeach 5 tankl of the series except the rst before admixins the solutionwith the solvent.

BENJAMIN T. BROOKS.

